Any of the .223 Wylde models will be able to fire .223 Remington or 5.56 NATO.
Hence it's description as a "long stroke" piston system. The best way to describe it is to describe what you see when you remove the BCG. It is attached to a long rod which ends with a removable piston that sits inside the exhaust chamber. Short stroke systems normally just cause push a rod which sits inside the receiver, to knock rather than blow the bolt back. These PWS systems are, in most opinions, far superior for many reasons. You'll need to look up that info. You won't go wrong with PWS.
Yes, you would just need to un-thread the installed muzzle device on the upper.
Yes it is.